The present invention relates to a television apparatus with a built-in video reproducing device for reproducing video signals from a recording medium, and in particular relates to a television apparatus with a built-in optical disk device suited for reproducing and displaying video signals recorded on an optical disk.
Television apparatuses with a built-in so-called video tape recorder, which uses magnetic tape as a recording medium of video signals and is capable of reproducing and displaying video images easily, are manufactured as products. On the other hand, there have been developed in recent years optical disk devices that record digital video signals on an optical disk, such as a compact disk read only memory (CD-ROM) or a magneto optical disk (MO), instead of on magnetic tape, and the digital video signals are read out by an optical pickup and subjected to digital signal processing to yield video signals.
As for optical disks, there are optical disks called photo CDs, optical disks called CD graphics, and optical disks called video CDs. In the case of photo CDs, natural pictures are recorded as still pictures and the natural pictures are read out, displayed as still images on a television apparatus, and electronically filed. In the case of CD graphics, graphic data are recorded in empty regions of music CDs (compact disks) and read out to reproduce sounds and graphic video images. In the case of video CDs, video signals of motion pictures (hereafter referred to as motion picture signals) are recorded and read out to display motion pictures on a television apparatus. Especially in video CDs, motion picture signals have been recorded as data-compressed digital signals.
In conventional VTRs, special regard has not been paid to dust because magnetic tape is used as a recording medium of video signals. On the other hand, when optical disks are used, sufficient regard should be paid to dust, because optical pickups are used. Furthermore, when optical disks are used, regard should be paid to noise as well, because digital signal processing circuits are used.
Furthermore, when a photo CD is reproduced and a still picture is displayed, a television display method of scanning a display screen 60 alternately along first scanning lines 61 and second scanning lines 62, each disposed every two lines, as shown in FIG. 1 is used. Therefore, the still picture flickers with a period of the alternate scanning of the first scanning lines 61 and the second scanning lines 62. In this case, line flicker thus becomes conspicuous. Furthermore, when motion picture signals, data-compressed according to MPEG (Motion Picture Expert Group) standards, are read out from a video CD to display motion pictures, there is a problem that block noise and mosquito noise become conspicuous, and the image quality is significantly degraded. These noises are caused by the motion picture signals having been subjected to digitization and data compression, and when motion pictures are to be displayed the motion picture signals are subjected to digital processing and then are subjected to signal processing in a video signal processing circuit in the same way as received video signals. Mosquito noise is caused in contour portions of images, whereas block noise is caused in remaining flat-luminance portions.
For example, in the case of a scene such as an automobile 70 moving in a direction indicated by an arrow as shown in FIG. 2, lattice block noise 72 is caused in a portion of the background 71 having a flat pattern, whereas mosquito noise 73, looking like flying insects, is caused in a boundary between the automobile 70 and the background 71.
In case of the MPEG standards, video signals are subjected to data compression processing for each of a plurality of regions that are obtained by dividing the screen. Each region is a block. If a block is thus used as the unit of data compression, a data value slightly different from its original value occurs between adjacent blocks when each block is subjected to data expansion processing to restore the original data value. On the display screen, therefore, such a lattice image as to set a frame to each block slightly occurs. This lattice image is the block noise.